Finite Element Modeling


The University of Houston-Downtown is in charge of the finite element analysis of the landing gear. In the Structural Analysis and Design Program, the analysis of structures under different loading and environmental conditions and its effects are the main source of research. The Concrete and Soil Laboratory counts with all the necessary equipment for the simulation of structures behavior in real world conditions. The students of Structural Analysis have built all the testing equipment which is a important key for the understanding of every different test. The students that are working on the project are:


The first step taken was to analyzed, in a rough draft at the beginning, the possible structural constraints that we might confront in a lunar environment. We found that the component acceleration tolerances were a crucial point so in response we started with a small test analyzing change in acceleration. This test was taken using a simple member under a constant load and falling from different heights. The environment for the test was selected taking in consideration the landing granular material which as we will mention later plays an important role in the acceleration and buckling requirements. Two accelerometers were attached to the top and bottom of the member in order to send electric signals in form of voltage, to get the different accelerations. The data acquisition program like excel 6.0 was used to get data from the member and then process in the computer. The different results obtained were compared. From this analysis we got to the conclusion that the spot for landing would decrease in great deal the problems due to components acceleration tolerances. Another important conclusion is that the shock due to impact on the landing process produces different magnitude of buckling load which determine the condition after landing of both the spacecraft and the internal equipment. These situations are only a few among many other structural reactions that will be analyzed in further tests. This initial test was only a warm-up to get our team in order . After this first step, our goal has expanded and every time we are coming out we new structural restrictions that we consider important to analyze in the landing gear model.

During the spring project review at Austin we discuss the communication problem between the groups. It is important to mention our progress in this aspect during the summer. We now have the opportunity to browse the Internet using Windows 95 Internet browser from our homes by dialing to the NT server at the lab. We can also share files from the lab network. We are using 28.8 fax modems.


We are now building a model of a landing gear using PVC material which will be tested at ultimate strength for dynamic loads effects. Once it is built we will also make a finite element analysis of the components, connections and joints before and after impact. The same model will be later built with different steel material and alloys type.

A linear programming technique will be used to calculate the minimum amount of material that will meet the requirements and will make it less expensive and least weight design. This technique consists on finding the minimum limits satisfying the requirements of the system. The linear programming is a method that is approached graphically by comparing in this case deflection vs. buckling of the members. The best selection for minimum weight will be found after getting the intercept of the minimum limits concerning the major structural constraints. This process will be done by a computer program upgraded to Visual Basic.

ANSYS will be used for the finite element analysis of the lunar landing gear. The finite element analysis will consists not only on the structural analysis but also in the dynamic and acoustic simulation of the landing and launch according to the data from the propulsion group.

The most important step by now is to get confident with the methodology and procedure to follow in order to be able to change dimensions and conditions, if required, for expected changes in the final designs. The team has also been reading literature concerning the project. For example about linear programming and also searching for some structural drawings.


The analysis for structural behavior is a very extensive complicated analysis which involves many hours and days of study. Due to the different responses to different conditions; our team has decided to start analyzing according to the material physical and mechanical properties already study in former designs developed in our laboratory.

The second step will be taking into consideration the components, connections and joints separately. For this finite element analysis we will be using ANSYS.

Soil Analysis:
The Soil analysis will be made later on with information of the data specimen of a real lunar granular soil. The effect on the impact and the stability of the spacecraft will be the objective for this section. This phase of our project will be done after the construction of the model and will be used for the simulation of the landing. Due to the shock absorbing properties of the granular material in many different parts of the moon, it will be important to select the landing place. Different changes in acceleration, buckling and spacecraft stability will be taken into consideration as well.

We are designing some structural drawings of landing gears in AutoCAD which we can send you some copies by next week. From these drawing we are going to chose one to build and to be tested.


In the next reports we will be giving data obtained from testing and further suggestion according to results. The major area of analysis will be the strength, acceleration, buckling and deformations occurred in the members of the landing gear individually and in group. We also could work and welcome any rough draft of a structural drawing of the landing gear, suggested by Lamar University.

From our home page you will be able to see pictures, data and any kind of information that we consider of interest by the other universities. We will be displaying the picture of our first model by next week in our Web page. Please if any questions please e-mail Andrea Struve.


Wednesday, 31-Dec-1969 18:00:00 CST
Comments to: author
Andrea StruveElectrical and Computer Engineering
Jose MaldonadoStructural Analysis and Design
Karla P. ReinaStructural Analysis and Design
Group Leader :
Dr. Alberto
Faculty member:
Jeff Border